Plate-type heat-exchange apparatus



Jan. 21, 1941. E, PREsTA g 2,229,306

PLATE-TYPE HEAT-EXCHANGE APPARATUS 3 Sheets-Sheet 1 Filed Aug. 4, 19358 INVN'I'DB EDWIN mesrnqs.

PLATE-TYPE HEAT-EXCHANGE APPARATUS Filed Aug. 4, 1938 3 Sheets-Sheet 2 Jig/,

INVEN TOR.

2H4 PRESTHGE. BY

ATTOR N E Y- Jan. 21, 1941- 1 E. PRESTAGE 2,229,306

PLATE-TYPE HEAT-EXCHANGE APPARATUS Filed Aug. 4, 1938 3 Sheets-Sheet 3 n-AVLNTOR. EDWIN PRES TAG E Patented Jan. 21, 1941 UNITED STATES PATENT OFFICE Application Augusta, 1938, Serial No. 223,080

In Great Britain August 5, 1937 v s 9' Claims. .This invention relates to plate-type heat-exchange units of the kind comprising a series of plates which are held together in a pack by clamping means, said plates having packing means interposed between the marginal parts of adjacent plates so that the innerparts of the plates are spaced to produce a plurality of thin, substantially flat chambers for the liquid to. be treated, said liquid being caused to flow in a 10 film substantially straight across each chamber from an inlet opening disposed adjacent one portion of the periphery of the chamber to an outlet opening adjacent the opposite portion of the periphery.

It is the object of the present invention to provide means in the construction" and operation of heat-exchange, units whereby their thermal efficiency may be increased, and by which such units are rendered more suitable for the heat treatment of milk and other liquids requiring a precise sequence and duration of the heat treat- 7 ment conditions. The present invention seeks to provide a form of apparatus which, for its size, is capable of treating a relatively large quan- 2 tity of liquid owing to the improved heat-exchange conditions existing therein. I

It has been found that with liquids, such as milk, the property of giving up heat to, or receiving heat from, the surface of a heat-exchange plate is largely dependent upon the velocity with which the liquid is flowing relative to the said surface. Moreover, there is a decided advantage in making the film of liquid between the plates relatively thin, i. e. of the order of 0.03" to 0.10", but this leads to practical difficulties in the. manufacture of the heat-exchange plates, mainly on account of the means which must be used to seal the marginal parts of the plates for preventing leakage It will be 40 observed that it is usual to form the seal by soft rubber washers set in relatively deep grooves. Also, there is'considerable commercial merit in using rolled sheet metal for the plates, mainly on account of the saving in weight and cost as compared with cast metal plates, and the perfectly smooth and sound condition in which sheet metal is now produced. Thermal conductivity of rolled sheet metal is also, greater than that of cast metal and this again improves the heat I transference,

According to the invention, regarded broadly, in a heat-exchange unit of the kind above referred to, the distance separating the inner parts of a pair of adjacent plates when the unit is in operation is substantially less than the disto, according to the invention the inner part tance separating their marginal parts. In all forms of heat-exchange unit according to the invention the reduced separation between the plates is measured in a direction at right angles to the general plane of the chamber-bounded by '5 said plates. The reduction in the separation can be produced in many ways, such as by causing the plates to be deflected by the pressureof the fluid used during operation, and by causing the clamping pressure to deform the plates and thus reduce their separation.

Heat-exchange units are already known in which the effective thickness of thechambers between the consecutive plates is made smaller than the thickness of the marginal packing means by making the plates conical in form, but such plates are not only relatively difficult to manufacture accurately, but require careful use and handling. Further, in a plate-type heatexchange unit wherein the liquids to be treated are caused to flow as a film through thin chambers bounded by adjacent plates, it has been proposed to form said plates with corrugations extending substantially transversely with respect to the direction of liquid flow, corresponding corrugations of consecutive plates being arranged to extend one into the other, causing the liquids to follow sinuous paths through the chambers, and also producing a sequence of constrictions the thickness of which'is smaller than the distance by which the plates are separated at their marginal parts. The total area of the constrictions in each chamber amounts however, to only a fraction of the areaof said chamber, and it will be noted that in these two forms of heat-exchange unit having conical and corrugated plates respectively, the separation of the plates at their inner parts, when measured at right angles to the general plane containing the marginal packing, i. e. the general planeof the plate in the case of the corrugated variety, is substantially equal to the thickness of said marginal packing means. I

In a heat-exchange unit of the kind referred of a plate is deflected or offset around its marginal part and just within the latter so that the thickness of the chamber between the said plate and the next adjacent plate, towards which the offsetting is directed, is substantially less than the thickness of the packing means between said plates. Thus, alternate plates may be dishshaped so as tocause the inner part of each to lie substantiallyrcloser' to one of the adjacent plates "than the distance separating the mar I co-pending natively, the thickness of the pack of plates forming the heat-exchange unit may be substantially less at the inner part than around the margin in order to make the thickness of each of the chambers less than the distance separating the distance of the marginal parts of the two plates bounding the chamber.

If desired, the pressure of cooling or heating fluid may be utilised to deflect the inner parts of the plates and thereby reduce the thickness of the film of liquid to be treated.

The invention is illustrated in the accompanying drawings in which Figures 1 and 2 are front elevations of a pair of plates to show the form of heat-exchange unit to which the invention relates; v

Figure 3 is a diagram to indicate the paths followed by the working fluids when the heat-exchange unit is in operation;

Figure 4 is a fragmentary sectional plan of one form of heat-exchange unit according to the invention, the plates being shown in the positions they occupy when theJunit-is inoperative;

Figurefi is a similar view showing the thin.

plates pressed over by the heating or cooling fluid;

Figure 6 is a similar view of an an arrangement in which the reduced separation between certain pairs of plates is obtained by the action of clamping the pack; v

Figure 7 is a fragmentary sectional plan of another form of heat-exchange unit in which all of the chambers are reduced in thickness by the action of the clamping means.

Figures 1, 2 and 3, which are taken from my application Serial No. 153,304,;tlled July 13, 1937, are included herein to exemplify the form of heat-exchange unit to which the present invention relates. Such a unit comprises a plurality of substantially flat plates having marginal packing means and adapted to be superimposed so that when they are clamped together they form a series of thin fluid-tight flat chambers across which the working fluids pass in the form of thin rapidly-moving fllms. In this example the plates are alternately thick and thin, a thick plate l0 being shown in Figure 1 and being provided around its front margin with a,

i1 and I8 are provided forthe passage of the working fluids and that spacing members I! which may be in the form of corrugations or applied strips are arranged longitudinally so that they do not interfere with the flow of the working-fluid from one end of the plate to the other. The arrangement of ports shown is intended to connect alternate chambers in series, but of.

course they may be placed .if desired so that alternate chambers are connected in parallel, as

both of these methods are quite well known. The views shown in Figures 4 to '7 are all fragmentary sectional plans to show various forms of improved heat-exchangerplate, and are those which would be obtained by/taking sections on a line '-.such as that shown at A-A in Figure l.'

ginal parts of the said adjacent plates. Alter- Referring to Figures 4 and 5 a series of, thick plates I0 and thin plates ii are arranged alternately, and their marginal parts are clamped together between a pair of massive end covers indicated at 20 and 2|, clamping means (not shown) such as screws or a hydraulic press being utilised to supply the requisite force. The thin plates l6 are relatively flexible by nature, and it will be seen that the spacing members I9 which ,are provided upon their inner parts project only slightly so that they do not contact with the thick plates II! as ,the heat-exchange unit is clamped up. The arrangement shown in Figures 4 and 5 is intended primarily for use where milk or an equivalent liquid is to be heated or cooled by a relatively inexpensive working fluid, such as hot water or brine respectively, and when the plates are assembled the usual inlet and outlet connections are arranged so that the chambers indicated at 22 are used to pass this hot water or brine,

the pressure being so adjusted that the thin with which the milk or equivalent liquid sweeps,

past the surfaces of the chamber, thus improving the rate of heat transfer, while it also tends to make the temperature of the milk or equivalent liquid more uniform during its passage through theheat-exchange unit.

The arrangement shown in Figure 6 is substantially the same as that in Figures 4 and 5, the

main difference being the provision of deflecting ribs or projections 3| which are attached to the thick plates i0 and are arranged to distort the relatively thin flexible plates l6 as the clamping pressure is applied by the end covers 20 and Bi. The thickness of thechambers 23 for the milk or equivalent is primarily determined by spacing members IS in the form of pressed-upribs, and these are preferably arranged to be out of register with the deflecting ribs 3| so that the flexibility of the thin plates l6 permits a certain amount of latitude in the degree to which the plates can be clamped together, thus allowing for the reduction in the thickness and resilience of the rubber packing rings l3 as these become old.

Another form of heat-exchange unit in which the desired reduction in the thickness of the chambers is obtained by the action of the clamping means is shown in Figure 7, and is particularly suitable for processes where a heat-exchange is to be efiected between hot milk or equivalent and cold milk or equivalent. Such heat-exchange units are employed primarily for economising heat, for example in the pasteurisation process, by causing a heat-interchange between the hot milk leaving a holding tank during emptying of the latter and the cold milk on its way towards another such tank which is being fllled. During the high-temperature short-time process the same stream of 'milk can of course be passed through both sets of chambers, said milk being held at the desired high temperature for the prescribed time after leaving one set of chambers and before entering the other'set. In this example the plates are indicated at 28 and are all relatively thin so as to be substantially flexible, each of said plates being formed at its marginal part with a grooved bead ill for the accommodation of i and in order to reduce the thickness of all of the chambers 22 and 23 the end cover 20 .is bulged.

as indicated at 32 so as to distort the plates 28 in the manner shown. Obviously, the outermost plates of the pack are deflected most, thus tending to limit the number of plates which can be used together. In the example shown however, an intermediate member 33 having both of its sides bulged at 32 is interposed within the pack so as to enable the number of plates 28 to be increased. Unribbed plates 34 are provided against the cover 20 and the appropriate side of the intermediate member so as to prevent the milk or equivalent liquid from coming into contact with said cover or intermediate member. The plates themselves are of course made from non-corrosive sheet metal, preferably stainless steel, although any suitable metal, such as nickel alloy or tinned copper, may be used. It will be understood that the sectional plan views in the,

drawings show only that part of the heat-exchange unit adjacent one side thereof, and therefore in the arrangements shown in Figures 5, 6 and 7 those parts of the chambers 22 and23 which lie immediately adjacent the marginal parts of the plates and which as a consequence are only partly reduced in thickness, constitute a relatively small portion of the total area of the chambers. It will be appreciated that by adopting th present invention the separation of the plates in a heat-exchange unit can be reduced to any desired extent, thus producing liquid films of or or even' thinner, despite the fact that the provision of a robust liquid tight rubber joint around the margins of the plates necessitates a relatively wide spacing at the margins of the plates.

What I claim is: I E

1. A heat-exchange unit -for liquids comprising a plurality of substantially fiat plates, clamping means for holding said plates together in a pack, resilient packing rings extending between the peripheral parts of adjacent plates to produce substantially fiat chambers, straight across which the liquids flow in fiat streams, said rings serving to seal the edges of said chambers, and at least some of said plates being flexible and adapted to be deflected by liquid pressure in the said chambers during operation of said unit, whereby to produce a thickness of the chamber between a pair of plates, for the major part of the area of said chamber, substantially less than the thickness of the packing ring between said pair of plates.

2. A heat-exchange unit comprising a plurality of metal plates, clamping means adapted to hold said plates in a pack, marginal packing rings separating the. edges of adjacent plates to define substantially flat liquid chambers, spacing said spacing members being substantially less in height than the thickness of the corresponding packing ring, so that when the heat exchange unit is in operation the pressure of the liquid therein will cause at least alternate plates to be deflected, whereby the thickness of the liquid chamber between said platesis made substantially less than the thickness of the correspond ing packing ring between said plates 3. A heat-exchange unit comprising a plurality of thin metal plates, clamping means arranged to hold said plates in a pack, marginal packing rings interposed between said plates to define liquid chambers, and means for squeezing said plates together at their center parts so that at least some of the chambershave for the major part of their area a thickness which is substantially less than thethickness of the packing ring serving to define said chamber.

4. Aheat-exchange unit comprising a plurality of plates, clamping means adapted to hold said plates, marginal packing rings installed between the edges of adjacent plates to define liquid chambers, across which the liquids flow in substantially fiat thin films, spacing projections distributed across the area of the plates and adapted to prevent adjacent plates from being brought into complete contact with one another, the clamping means being arranged to compress the center parts-of the plates to a greater extent than the peripheral portions thereof, whereby the thickness 01' each or the chambers is reduced to a value which is less than the thickness of the packing ring defining the margin ofsaid .chamber.

5. A heat-exchange unit comprising a series of thin sheet metal plates, clamping means securing said plates in a pack, marginal packing means serving to hold said plates apart and defining thin substantially flatJchambers for the liquids to be treated, all of said plates having their marginal parts ofiset so that when the heat-exchange unit is in operation the thickness of the chamber'between a pair of contiguous plates is substantially less than the thickness of .the packing ring disposed between said two plates. a

6. A heat-exchange unit comprising a plurality of thin metal plates, clamping means arranged to hold said plates in a pack, marginal ,packing rings interposed between said plates'defining liquid chambers, means for squeezing said plates together at their center parts so that at least some of the chambers have .i'or the major part 01' their area a thickness which is substantially less than the thickness of the packing ring serving to define said chamber, and a separating member dividing the pack of plates into sections, and which is thinner at its peripheral part means will cause deflection of the flexible plates to reduce the thickness of the adjacent liquid chamber to a value which is less than the thicky Y ness of the packing ring defining the margin of members distributed over the area of the plates,

the'said adjacent liquid chamber.

8. A heat-exchange unit for liquids comprising a plurality of substantially flat plates, clamping means for holding said plates together in a pack, resilient packing rings extending between the peripheral parts of adjacent plates to produce substantially flat chambers permitting liquid to fiow thereacross in thin flat streams, said ringsserving to seal the edges of said chambers, and at least some of the plates being flexible and adapted to be deflected towards the next adjacent plate when the unit is assembled and put into operation, whereby to produce a thickness of chamber between a. pair of plates for the major part of the area of said chamber substantially less than the thickness of the packing ring between said pair of plates.

9. A heat-exchange unit comprising a plurality of flexible metal plates, clamping means adapted to hold said plates in a pack, marginal packing rings separating the edges 01 adjacent plates to define substantially flat liquid chambers, spacing members distributed over the area of the plates, said spacing members being substantially less in height than the thickness or the corresponding packing ring, and means for deflecting at least alternate plates when the heatexchange unit is assembled and placed in operation, whereby the thickness of the liquid chamber between said plates is made substantially less than the thickness of the corresponding packing ring between said plates.

EDWIN PRESTAGE. 

